package eiisan.lock;

import java.io.Serializable;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;

/**
 * 不可重入 独占锁
 *
 * @author eii
 * @time 2020/10/17 10:49 下午
 */
public class NonReentrantLock implements Lock, Serializable {

    private static class Sync extends AbstractQueuedSynchronizer {
        //是否锁已经被持有
        @Override
        protected boolean isHeldExclusively() {
            return getState() == 1;
        }

        //如果state为0 则尝试获取锁
        @Override
        protected boolean tryAcquire(int arg) {
            assert arg == 1; //
            if (compareAndSetState(0, 1)) {
                setExclusiveOwnerThread(Thread.currentThread());
                return true;
            }
            return false;
        }

        //尝试释放锁，设置state为0
        @Override
        protected boolean tryRelease(int arg) {
            assert arg == 1; //
            if(getState() == 0){
                throw new IllegalMonitorStateException();
            }
            setState(0);
            setExclusiveOwnerThread(null);
            return true;
        }

        //提供条件变量接口
        Condition newCondition(){
            return new ConditionObject();
        }
    }

    private final Sync sync = new Sync();

    @Override
    public void lock() {
        sync.acquire(1);
    }

    @Override
    public boolean tryLock() {
        return sync.tryAcquire(1);
    }

    @Override
    public void unlock() {
        sync.release(1);
    }

    @Override
    public Condition newCondition() {
        return sync.newCondition();
    }

    @Override
    public void lockInterruptibly() throws InterruptedException {
        sync.acquireInterruptibly(1);
    }

    @Override
    public boolean tryLock(long timeount, TimeUnit unit) throws InterruptedException {
        return sync.tryAcquireNanos(1,unit.toNanos(timeount));
    }

}
